1. Field of the Invention
The present invention relates generally to a circuit-terminal connecting device, and more particularly to an improvement in a circuit-terminal connecting device used for connecting first circuit-terminals provided on a mail circuit board with second circuit-terminals provided on a flat circuit member, such as a flexible printed circuit board (hereinafter, referred to as an FPC), which is mounted on the main circuit board to be electrically coupled with the main circuit board.
2. Description of the Prior Art Including Information Disclosed Under 37 CFR 1.97 and 37 CFR 1.98
There has been proposed, for the purpose of saving a space in an electronic apparatus, to lay a flat circuit member, such as a relatively small-sized FPC, on top of a main circuit board on which various electrical or electronic parts are mounted when the flat circuit member is electrically coupled with the main circuit board in the electronic apparatus. Such an electrical coupling between the main circuit board and the flat circuit member wherein the flat circuit member is laid on top of the main circuit board is hereinafter referred to as an electrical piled coupling.
There have been also previously proposed several means for connecting a plurality of circuit-terminals provided on a flat circuit member, such as an FPC, respectively with a plurality of another circuit-terminals provided on a main circuit board in a condition wherein the main circuit board and the flat circuit member are put in the electrical piled coupling. With one of such means previously proposed, there has been constituted a circuit-terminal connecting structure in which an electrical connector having an insulated housing is mounted on a main circuit board, a flat circuit member is provided with a reinforced portion attached to a reinforcing board, and the reinforced portion of the flat circuit member attached to the reinforcing board is directly engaged with the insulated housing of the electrical connector so that a plurality of circuit-terminals provided on the reinforced portion of the flat circuit member are connected respectively with a plurality of circuit-terminals provided on the main circuit board, as disclosed in, for example, the Japanese patent application published before examination under publication number HEI 6-68940 (hereinafter, referred to as a published prior art document 1).
In the circuit-terminal connecting structure disclosed in the published prior art document 1, an electrical connector (a connector (3)) having an insulated housing (an insulator (30)) provided to be fixed to a main circuit board (a printed circuit board) is mounted on the main circuit board and a flat circuit member (an FPC cable (1)) has a reinforced portion thereof which is reinforced with a reinforcing board member (2). The insulated housing (30) of the electrical connector (3) is provided with a board member holding portion on which a plurality of contacts (33) are arranged and by which the reinforced portion of the flat circuit member (1) is held. A pair of board member locking portions (locking members (37)) are provided to stand respectively at a pair of end portions of the board holding portion in a direction along which the contacts (33) are arranged (a contact-arrangement direction) so that the contacts (33) are arranged between the board member locking portions (37) opposite to each other. An engaging hole (37a) is formed on each of the board member locking portions (37).
The reinforced portion of the flat circuit member (1) is provided with a plurality of circuit-terminal s arranged on a lower surface thereof and the reinforcing board member (2) attached to an upper surface thereof. The reinforced portion of the flat circuit member (1) with its lower surface on which the circuit-terminals are arranged is held, together with the reinforcing board member (2) attached thereto, by the board member holding portion of the insulated housing (30) of the electrical connector (3). The reinforcing board member (2) is provided with a pair of projections (engaging projections (23) formed respectively at a pair of end portions thereof in its longitudinal direction extending to be coincide with the contact-arrangement direction when the reinforcing board member (2) is held by the board member holding portion of the insulated housing (30).
When the reinforced portion of the flat circuit member (1) with the reinforcing board member (2) attached to the upper surface of the reinforced portion is held by the board member holding portion of the insulated housing (30) of the electrical connector (3), the contacts (33) arranged on the board member holding portion of the insulated housing (30) and soldered respectively to a plurality of circuit-terminal s of the main circuit board are caused to come into resilience-contact with the circuit-terminals arranged on the reinforced portion of the flat circuit member (1). Further, the projections (23) formed at the end portions of the reinforcing board member (2) attached to the reinforced portion of the flat circuit member (1) are put in engagement respectively with the engaging holes (37a) formed on the board member locking portions (37) standing respectively at the end portions of the board holding portion. Thereby, the end portions in the longitudinal direction of the reinforcing board member (2) are locked respectively by the board member locking portions (37) so that it is expected that a condition wherein the contacts (33) arranged on the board member holding portion of the electrical connector (3) are put in resilience-contact with the circuit-terminals arranged on the reinforced portion of the flat circuit member (1) is stably maintained.
When the end portions in the longitudinal direction of the reinforcing board member (2) are locked respectively by the board member locking portions (37) as described above in the circuit-terminal connecting structure disclosed in the published prior art document 1, the reinforced portion of the flat circuit member (1) and the reinforcing board member (2) attached thereto are resiliently pushed up from the side of the lower surface of the reinforced portion of the flat circuit member (1) by the contacts (33) arranged on the board member holding portion of the insulated housing (30) of the electrical connector (3). Thereby, it is feared that the reinforced portion of the flat circuit member (1) and the reinforcing board member (2) attached thereto are compulsorily curved so that a middle portion between the end portions in the longitudinal direction of the reinforcing board member (2) protrudes to go away from the board member holding portion of the insulated housing (30). If the reinforced portion of the flat circuit member (1) and the reinforcing board member (2) attached thereto are practically subjected to a condition to be curved as mentioned above, for example, the circuit-terminals arranged on the reinforced portion of the flat circuit member (1) are adversely affected by the curve brought about on the reinforced portion of the flat circuit member (1) and the reinforcing board member (2) attached thereto.
Accordingly, there has been further previously proposed an improved circuit-terminal connecting structure which is able to avoid the disadvantages accompanied with the above-described circuit-terminal connecting structure disclosed in the published prior art document 1, as disclosed in, for example, the Japanese patent application published before examination under publication number 2012-252912 (hereinafter, referred to as a published prior art document 2).
In the circuit-terminal connecting structure disclosed in the published prior art document 2, when a reinforced portion of a flat circuit member (a FPC cable (301)) is held, together with a reinforcing board member (a reinforcing board (304)), by a board member holding portion of an insulated housing (a housing (102)) of an electrical connector (a flat cable connector (101)) mounted on a main circuit board (a circuit board (201)), a pair of end portions in a longitudinal direction of the reinforcing board member (304) are locked respectively by a pair of board member locking portions (locking portions (103)) provided on the insulated housing (102). Under such a condition, a plurality of contacts (contacts (105)) arranged on the board member holding portion of the insulated housing (102) of the electrical connector (101) along the longitudinal direction of the reinforcing board member (304) and soldered respectively to a plurality of circuit-terminal s of the main circuit board (201) are caused to come into resilient-contact with a plurality of circuit-terminals (terminals (302A)) arranged on the reinforced portion of the flat circuit member (301). Thereby, the reinforced portion of the flat circuit member (301) and the reinforcing board member (304) attached thereto are resiliently pushed up from the side of a lower surface of the reinforced portion of the flat circuit member (301) by the contacts (105) arranged on the board member holding portion of the insulated housing (102) under the condition wherein the end portions in the longitudinal direction of the reinforcing board member (304) are locked respectively by the board member locking portions (103) provided on the insulated housing (102).
The reinforcing board member (304) attached to the reinforced portion of the flat circuit member (301) is provided, at one of side ends each extending in a longitudinal direction of the reinforcing board member (304), with a bent portion (an engaging projection (304E)) spreading over the side ends. The bent portion (304E) is operative to prevent the reinforcing board member (304) from being curved in the longitudinal direction of the reinforcing board member (304). As a result, even if the reinforced portion of the flat circuit member (301) and the reinforcing board member (304) attached thereto are resiliently pushed up from the side of the lower surface of the reinforced portion of the flat circuit member (301) by the contacts (105) arranged on the board member holding portion of the insulated housing (102) under the condition wherein the end portions in the longitudinal direction of the reinforcing board member (304) are locked respectively by the board member locking portions (103) provided on the insulated housing (102), the reinforced portion of the flat circuit member (301) and the reinforcing board member (304) attached thereto are prevented, by the bent portion (304E) provided at the side end of the reinforcing board member (304) to spread over the same, from being caused to curve in the longitudinal direction of the reinforcing board member (304) so that a middle portion between the end portions in the longitudinal direction of the reinforcing board member (304) is also prevented from protruding to go away from the board member holding portion of the insulated housing (102).
In the case of such a previously proposed circuit-terminal connecting structure used as disclosed in the published prior art document 2 in which the circuit-terminal s provided on the flat circuit member are caused to come into contact respectively with circuit-terminals provided on the main circuit board under the condition wherein the main circuit board and the flat circuit member are put in the electrical piled coupling, it is also desired to reduce as much as practicable a thickness of the electrical connector mounted on the main circuit board and therefore it is considered to make the insulated housing of the electrical connector relatively thin so that the electrical connector is subjected to reduction in thickness.
When the insulated housing of the electrical connector is made to be relatively thin so as to reduce the thickness of the electrical connector, the stiffness of the insulated housing is also reduced undesirably. Under a condition wherein the insulated housing of the electrical connector is made to be relatively thin, when the reinforcing board member attached to the reinforced portion of the flat circuit member is provided with the bent portion spreading over the side end extending in the longitudinal direction of the reinforcing board member and thereby the reinforced portion of the flat circuit member and the reinforcing board member attached thereto are prevented, by the bent portion provided at the side end of the reinforcing board member, from being caused to curve in the longitudinal direction of the reinforcing board member so that the middle portion between the end portions in the longitudinal direction of the reinforcing board member is also prevented from protruding to go away from the board member holding portion of the insulated housing even if the reinforced portion of the flat circuit member and the reinforcing board member attached thereto are resiliently pushed up from the side of the lower surface of the reinforced portion of the flat circuit member by the contacts arranged on the board member holding portion of the insulated housing under the condition wherein the end portions in the longitudinal direction of the reinforcing board member are locked respectively by the board member locking portions provided on the insulated housing, a resilient press-force caused to act on the reinforced portion of the flat circuit member and the reinforcing board member attached thereto by the contacts arranged on the board member holding portion of the insulated housing brings about a reactive force acting on the insulated housing. With such a reactive force thus brought about, it is feared that the insulated housing with its stiffness undesirably reduced is compulsorily curved so that a middle portion between a pair of end portions of the insulating housing opposite to each other in a longitudinal direction of the insulating housing along which the contacts are arranged protrudes to go away from the flat circuit member and the reinforcing board member attached thereto.
In the case where the insulated housing with its stiffness undesirably reduced is compulsorily curved in such a manner as mentioned above, an undesirable stress is inflicted on soldering portions on the main circuit board at which the contacts arranged on the insulated housing are soldered respectively to the circuit-terminals provided on the main circuit board and thereby it is feared that undesirable cracks are brought about on the soldering portions.